The existing fellowship program in Pediatric Emergency Medicine at Children's Hospital (CH) has been dedicated to the preparation of academic investigators for a career in emergency medicine research. The training outlined in this proposal will build on the outstanding past experience of the fellowship in graduating productive and committed investigators. Fundamental features of the proposed Research Training Program include direct research participation in conjunction with a comprehensive curriculum of didactic instruction and enrichment activities to provide a deep foundation in modern techniques for clinical investigation and biomedical science. A) Research Tracks, Disciplines, and Themes (Figure 1, page 72). Trainees will undertake training in one of three tracks: 1) clinical investigation, 2) medical informatics or 3) basic science. The trainees in clinical investigation will acquire skills in the disciplines of biostatistics, clinical epidemiology, health outcomes research/quality control and clinical laboratory research (translational research). Those pursuing medical informatics will study the disciplines of data mining, data modeling, use of controlled medical vocabularies, programming web-based applications, and designing automated decision support systems. Disciplines for basic science trainees will include molecular biology, cellular immunology, physiology and pharmacology. The tools acquired through mastery of these disciplines will be applied to studies addressing specific themes in Pediatric Emergency Medicine for which members of the training faculty have established expertise: Clinical Effectiveness/Medical Decision Making, Infectious Diseases, Immunology, Pulmonology (Asthma), Hematology (Sickle cell anemia), Trauma, Pharmacology, and Medical Toxicology/Environmental Health. B) Level of Training, Background and Numbers of Trainees. This application proposes post- doctoral training. Eight post-doctoral positions are requested; two post- doctoral fellows will begin training each year and remain in research training for a minimum of two or three years (depending on track), supported by this award. C) Training Facilities. Research training will take place under the mentorship of a group of established investigators with extensive existing interactions at CH, Harvard Medical School (HMS), The Channing Laboratory of Brigham and Women's Hospital, Harvard School of Public Health and MIT. Laboratories are present at the Enders Research Building at CH, The Harvard Medical School and The Channing Laboratory. Didactic educational programs will include those offered within the Division of Pediatric Emergency Medicine, and through HMS, Harvard School of Public Health, MIT and Harvard University.